resolvconf-admin
resolvconf-admin is a setuid helper program for tools that need to
be able to set up the local DNS resolver configuration.
This program deals with setting the local DNS resolver configuration
(i.e. /etc/resolv.conf), which needs to be done as root on some
systems. One example use case is to run a DHCP client without giving
that DHCP client full superuser privileges.
Theory of Operation
If /sbin/resolvconf is present and executable, it is invoked as root
with the specified configuration. If /sbin/resolvconf is not
present (or is present but not executable), then /etc/resolv.conf is
updated directly.
WARNING!!!
A better approach for setting up the DNS in a non-privileged way is to
make an authenticated IPC call to some running daemon that already
manages
/etc/resolv.conf.
However, some systems do not run such a daemon, so we offer this
setuid approach instead, for those limited systems only.
This setuid program should not be installed on systems that already run such a daemon, because every setuid program increases the attack surface of the operating system.
DO NOT INSTALL THIS TOOL IF YOU HAVE BETTER OPTIONS AVAILABLE TO YOU!
Installation
It should probably be installed as /usr/bin/resolvconf-admin
something like this:
getent group resolvconf-admins >/dev/null || addgroup --system resolvconf-admins
chown root:resolvconf-admins /usr/bin/resolvconf-admin
chmod 4754 /usr/bin/resolvconf-admin
and then make sure the user that you care about has access, by adding them to this group:
adduser my-nonpriv-dhcp-daemon resolvconf-admins
Usage
When the non-privileged user wants to set local DNS resolvers due to information it learned from interface NETIF, it should invoke:
resolvconf-admin add NETIF [-s SEARCH] [-d DOMAIN] NAMESERVER [...]
Note that DNS search path and domain name are optional. However, at least one nameserver is required.
When the non-privileged user wants to tear down the DNS resolver information that it had previously set for interface NETIF, it should invoke:
resolvconf-admin del NETIF